The present invention generally pertains to strip chart recorders and is particularly directed to improvements therein that enhance their usage and make them less costly to assemble.
Strip chart recorders are used to record variations in a sensed predetermined variable condition over a period of time. A typical strip chart recorder includes a case having a base and a cover, and containing a chart dispenser; a platen; means for advancing a chart from the chart dispenser across the platen; a transducer for sensing a predetermined variable condition; and marking means coupled to the transducer, with the marking means being disposed for marking that portion of the chart that is being advanced across the platen in a lateral position that is dependent upon the state of the sensed predetermined variable condition. Various prior art strip chart recorders are described in U.S. Pat. Nos. 4,222,061 and Re.30,512 to John C. Stires, III; Re.32,108 and 3,971,035 to Maxwell; 4,135,400 to Maxwell et al; 3,221,321 to Hashimoto; 1,443,732 to Cook; 2,557,437 to Jepson; 3,140,144 to Koch et al; 3,200,403 and 3,388,404 to Bush; 3,787,885 to Johnson; and 4,044,362 to Greenhut.
Some of the prior art strip chart recorders include certain additional desirable features, such as a writing table mounted in the base combined with a window in the cover and a lid for closing the window, with the window being disposed over the writing table for enabling that portion of the chart that has been advanced over the writing table to be written upon after the cover has been closed; means for sealing the cover in a closed position, whereby the recorder provides sealable access to that portion of the chart that is over the writing table when the cover is closed and the window is open; means on the inside of the cover for automatically latching the lid in a closed position upon the lid being closed combined with means on the inside of the cover for releasing the latching means, whereby, upon being latched, the lid can be opened again only after the cover is opened; the platen and the writing table being provided by a continuous surface of a single chassis; a chassis defining a chamber for receiving a battery having a given shape, combined with electrical contacts within the chamber for connection to the battery to enable the battery to power the advancing means; a peg being disposed on the lid for entering the case and peg engaging means for actuating the chart advancing means when the cover is closed; the chart dispenser including a chart chamber, having a wall including an opening through which a tightly rolled chart may be inserted laterally; the chart advancing means including a motor, such as a rotary stepping motor, means for periodically actuating the motor, a chart take-up spool for receiving the end of the chart that has been fed from the chart dispenser, and a gear train coupling the spool to the motor for rotating the spool to advance the chart upon each actuation of the motor; the transducer being mounted in the cover; the transducer including a bimetal coil; and the marking means including a stylus coupled to the bimetal coil for marking the chart.
Typically, the design of the prior art strip chart recorders is such that their assembly is highly labor intensive and thereby quite expensive.
It is an the object of the present invention to provide a strip chart recorder that affords certain desirable features of prior art strip chart recorders, but yet is of such design that its assembly is less expensive.